Navigation device

ABSTRACT

A navigation device includes a map information storage means for storing map information such as nodes, links and the like, a present position detection means for detecting a present position of a moving body, a route searching means for searching a route from a present position to a guide point based on the map information, a voice guide message generation means for generating a voice guide message corresponding to the searched route, and a voice output means for outputting the voice guide message. The navigation device is adapted to store a level of importance of nodes and links as a part of said map information, and the voice guide message generation means selects links and nodes on the searched route based on the level of importance and generates a voice guide message corresponding to the selected nodes and links.

CROSS-REFERENCE TO THE RELATED APPLICATION

[0001] This application is a continuation of international ApplicationNo. PCT/JP99/02748, whose international filing date is May 25, 1999, thedisclosures of which Application are incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a navigation device which ismounted in a moving body and which guides a route from a presentposition to a destination.

[0004] 2. Description of Related Art

[0005] Navigation devices which guide a route from a current position ofan automobile to a destination while driving have been widely applied.In this type of navigation device, when a destination is set by a user,the device searches a preferred route from the current position to thedestination. When the searched route is presented to a user, it iscommon to present the route in an “entire route format” in which a routefrom a geographical position, at which a destination is set, to thedestination is displayed on the same screen by switching a map scale.Furthermore, a method is employed of displaying more detailedinformation about the route by scrolling the map display automaticallyor manually along the route by switching to a detailed map display witha large map scale ratio. In addition, a method of sequential display ofguiding maps of intersections on the route forward of a currentposition, or a method of displaying the route schematically by mainbranching points on the display device are also known in the art.Furthermore, it is possible to execute the guiding operation by use ofvoice commands.

[0006]FIG. 1 is a block diagram showing a first conventional navigationdevice as disclosed in JP-A-5-297800. In the figure, reference numeral 1denotes a touch switch for inputting a destination or the like, 2 is avehicle speed sensor for detecting a vehicle speed, 3 is a bearingsensor for detecting a bearing, 4 is an external storage device forstoring information displaying classes of roads connecting branchingpoints or information displaying classes of branching point of roads andpre-stored map information data. 5 is a display device for displayinginformation regarding main points such as branching points which are ona route from the present position to the destination. 6 is a controldevice which searches a travel route of the vehicle based on an inputsignal from the bearing sensor 3 and the vehicle sensor 2 and an inputsignal from the switch 1 and which displays main branching points on thetravel route in summary form on the display device 5.

[0007] The operation of the first conventional navigation device will bedescribed below.

[0008] Firstly, route searching is executed. The route searching isexecuted according to a Dijkstra method. Of the routes connecting thepresent position and the destination, the device searches a routepassing along main roads in which there are few right or left turns andin which the names of intersections at which turns are made are known.The search is made on the basis of the map information data stored inthe external storage device 4.

[0009] After the route is searched, the number of nodes contained on theroute is counted and it is determined whether the number of nodes isless than or equal to 10. When the number of nodes is less than or equalto 10, the display process is executed to display the searched route.

[0010] On the other hand, when there are more than 10 nodes, asummarizing process is applied to the nodes contained on the route inwhich they are summarized based on informational value of each node. Thesummarizing process entails deleting those nodes of low informationvalue until the number of nodes contained on the route are less than orequal to 10. Thereafter, display processing is executed. Hereininformation value is a product of a turning coefficient, a namepresence/absence coefficient and a node category coefficient. The nodecategory coefficient is a fixed coefficient corresponding to categoriesof nodes such as expressway entrance/exit, tollway entrance/exit ornational road intersection. The node name presence/absence coefficientis a fixed coefficient which corresponds to the presence or absence of aname of the node. The turning coefficient is a fixed coefficient whichcorresponds to the presence or absence of left or right turns.

[0011] In the display process, the name of the destination and presentposition, the name of main branching points on the route from thepresent position to the destination, the distance between each branchingpoint, representative place names which indicate the direction oftravel, and the names of roads which should be taken at branching pointsare displayed on the display device 5.

[0012]FIG. 2 is a block diagram of a second conventional navigationdevice as disclosed in International Publication WO98/51995. In thefigure, reference numeral 10 denotes a control means which performscontrol of the overall device and each type of calculation in thenavigation device. 11 is a map information storage means which storesdigitized map information data such as intersection data, road data andthe like. 12 is a present position detection means which detects apresent position of the moving body in which the navigation device ismounted.

[0013]13 is a route setting means which sets a route between two pointson a map on the basis of map information data stored in the mapinformation storage means 11. 14 is a guide object intersectiondetection means which detects a guide object intersection to be guidedon the route set by the route setting means 13. 15 is a quantizingcalculation means which quantizes the route of the moving body onto aschematic map displaying the characteristic features of the route.

[0014]16 is a display means which displays a route quantized by thequantizing calculation means with respect to a guide object intersectiondetected by the guide object intersection detection means 14. 17 is avoice guide message generation means having a voice information storagemeans (not shown) which stores necessary words or phrases for guidemessages as voice wave form data. The voice guide message generationmeans selects voice wave form data such as words or phrases for guidemessages and generates such combinations as guide messages when aquantized route of the moving body is displayed on the display means 16.18 is a voice output means which notifies a user by voice commands ofguide messages generated by the voice guide message generation means.

[0015] The operation of the second conventional navigation device willbe described below.

[0016]FIG. 3 is a flowchart explaining the operation of the secondconventional navigation device shown in FIG. 2.

[0017] Firstly, in a step ST1, the route setting means 13 sets twopoints on the map on the basis of latitude and longitude from the mapinformation data read from the map information storage means 11 and thensets a route between the two points using a general search algorithm ona network such as a Dijkstra method or the like.

[0018] Then, in a step ST2, the present position detection means 12detects a present position (C1) of the moving body. In a step ST3, theflags FL1, FL2, FL3 are respectively initialized to 0.

[0019] Then, in a step ST4, the guide object intersection detectionmeans 14 extracts an intersection with, for example, more than threeroads being connected to the intersection as a forward guide objectintersection (C2). The intersection is an intersection on the route setby the route setting means 13 and, of the two geographical points set bythe route setting means, the intersection is further forward thanpresent position (C1) detected by the present position detection means12.

[0020] In the step ST5, the detection of the present position (C1) ofthe moving body is performed again by the present position detectionmeans 12 and in a step ST6, a road distance (L1) between the presentposition (C1) of the moving body and the forward guide objectintersection (C2) is calculated on the basis of map information dataread from the map information storage means 11.

[0021] Then, in a step ST7, further processing operations are selectedin response to this distance (L1).

[0022] When the distance (L1) is greater than a predetermined referencedistance (L2) (for example 1000 meters), the routine progresses to stepST8 and it is determined whether the flag FL1 has a value of 0 or not.When the value of the flag is 0, in a step ST9, a guide output A whichis related to the forward guide object intersection (C2) is executed.The guide output A comprises extracting only the section to the forwardguiding object intersection (C2) extracted by the quantizing calculationmeans 15 of the road on the route on the map. Then, the result isquantized to a simple arrow shape and a display map related to theforward guide object intersection (C2) is displayed on the display means16. A guide voice message related to the forward guide objectintersection (C2) is generated by the voice guide message generationmeans 17 and the message is reported by voice commands from the voiceoutput means 18. After the execution of the guide output A, in a stepST10, the flag FL1 is varied to a value of 1 and the fact that the guideoutput A in relation to the forward guide object intersection (C2) hasbeen executed is stored.

[0023] Thereafter, in a step ST11, it is determined whether or not theprocess of setting the route by the route setting means 13 is completed.When it is completed, the guide process is terminated. When it is notcompleted, the routine returns to a step ST5 and executes the steps ofthe routine after step ST6.

[0024] When the flag FL1 does not have a value of 0 in step ST8, sincethe guide output A has already been executed, the routine returns to astep ST5.

[0025] In a step ST7, when the distance (L1) is less than or equal tothe reference value (L2) and greater than the predetermined referencevalue (L3) (for example 300 meters), the routine progresses to a stepST12, and it is determined whether or not the flag FL2 has a value of 0.When the flag FL2 has a value of 0, in the step ST13, a guide output Brelated to the forward guide object intersection (C2) is executed. Theguide output B comprises extracting only the route section connectingthe forward guiding object intersection (C2) of the road on the mapextracted by the quantizing calculation means 15. Then, the result isquantized to a simple arrow shape and a display map related to theforward guide object intersection (C2) is displayed on the display means16. A guide voice message related to the forward guide objectintersection (C2) is generated by the voice guide message generationmeans 17 and the message is reported by voice commands from the voiceoutput means 18. After the execution of the guide output B, in a stepST14, the flag FL2 is varied to a value of 1 and the fact that the guideoutput B in relation to the forward guide object intersection (C2) hasbeen executed is stored.

[0026] Thereafter, in a step ST11, it is determined whether or not theprocess of setting the route by the route setting means 13 is completed.When it is completed, the guide process is terminated. When it is notcompleted, the routine returns to a step ST5 and executes the steps ofthe routine after step ST6.

[0027] When the flag FL2 does not have a value of 0 in step ST12, sincethe guide output has already been executed, the routine returns to astep ST5.

[0028] When, in a step ST7, the distance (L1) has a value less than thereference value (L3), the routine progresses to a step ST15 and it isdetermined whether or not the flag FL3 has a value of 0 or not. When thevalue of the flag is 0, in a step ST16, the guide output C related tothe forward guide object intersection (C2) is executed. The guide outputC comprises extracting the present position of the moving body, roadsother than roads on the route, route roads connected to the forwardguiding object intersection (C2) and the forward guiding objectintersection (C2) extracted by the quantizing calculation means 15 onthe map. Then, the result is quantized to a simple arrow shape and adisplay map related to the forward guide object intersection (C2) isdisplayed on the display means 16. A guide voice message related to theforward guide object intersection (C2) is generated by the voice guidemessage generation means 17 and the message is reported by voicecommands from the voice output means 18. After the execution of theguide output C, in a step ST17, the flag FL3 is varied to a value of 1and the fact that the guide output C in relation to the forward guideobject intersection (C2) has been executed is stored.

[0029] Thereafter, in a step ST11, it is determined whether or not theprocess of setting the route by the route setting means 13 is completed.When it is completed, the guide process is terminated. When it is notcompleted, the routine returns to a step ST5 and executes the steps ofthe routine after step ST6.

[0030] When the flag FL3 does not have a value of 0 in step ST15, sincethe guide output C has already been executed, the routine returns to astep ST3, and the flags FL1, FL2, FL3 are initialized to 0. In a stepST4, the forward guide object intersection (C2) is extracted.

[0031] Since the conventional navigation device is constructed as above,the problem has arisen that safe operation of the vehicle can beaffected as it is necessary for a user to monitor the guide display evenwhen display nodes are displayed in summary form by a summarizingprocess. Furthermore, the number of guiding nodes provided to guide theentire route by voice commands increases and the problem has arisen thatnodes can not be adapted to guide the entire route appropriately in ashort time.

[0032] Furthermore, when the number of guide nodes is reduced to apredetermined number of summarized nodes in a convention navigationdevice, the problem has arisen that it is difficult to make guide nodescorrespond to a predetermined number of nodes when a plurality of nodeswith the same informational value exists.

SUMMARY OF THE INVENTION

[0033] The present invention is proposed to solve the above problems andhas the object of providing a navigation device adapted to store thelevel of importance of nodes and links and select nodes and links on thesearched route based on the level of importance or time for playingvoice information. In the navigation device, a voice guide message isgenerated corresponding to the selected nodes and links and guiding ofthe route is executed by the voice guide message. Thus, it is possibleto guide an entire route appropriately in a short time by voicecommands.

[0034] The present invention has the further object of providing anavigation device in which when a plurality of nodes and links with thesame importance exists and the number of such nodes and links is notequal to a predetermined reference number, nodes and links in proximityto the present position, the number of which corresponds with thepredetermined reference number, is selected from nodes and links withthe same importance, thereby to make the number of guide nodes and thelike accurately correspond with the predetermined reference number.

[0035] A navigation device of the present invention is adapted to storea level of importance of each node and link as a part of map informationin a map information storage means, to select the nodes and links on thesearched route based on the level of importance and to generate a voiceguide message corresponding to the selected links and nodes. In thisway, it is possible to guide an entire route appropriately in a shortperiod of time by voice commands.

[0036] The navigation device of the present invention may be adapted toselect the nodes and links on the searched route in such a manner thatthe level of importance of the selected nodes and links is less than orequal to a predetermined reference level and the number of the selectednodes and links is less than or equal to a predetermined referencenumber, and to generate a voice guide message corresponding to theselected nodes and links. In such a way, even when the number of nodesand links with a high level of importance is less than a predeterminedreference number, the voice guiding with respect to the nodes and linkshaving low level of importance is not executed. Thus, it is possible toguide the entire route appropriately.

[0037] The navigation device of the present invention may be adapted todelete nodes and links, which are located in proximity to the guidepoint, from the nodes and links having the same level of importance andto make the number of the selected nodes and links equal to apredetermined reference number, when there exists a plurality of nodesand links with the same level of importance and the number of theselected nodes and links is not equal to the predetermined referencenumber. In this way, it is possible to make the number of nodes andlinks to be guided correspond accurately with the predeterminedreference number.

[0038] The navigation device of the present invention may be providedwith a reference value setting means for setting a predeterminedreference value and a reference number setting means for setting apredetermined reference number. In this way, it is possible to provide avoice guide with the desired amount and level of importance.

[0039] The navigation device of the present invention may be adapted tostore information about voice playing times relating to names of eachlink and node as a part of map information in the map informationstorage means, to select the nodes and links on the searched route inorder of highest importance in such a manner that the voice playing timefor the voice guide message is less than or equal to a predeterminedreference value, and to generate the voice guide message correspondingto the selected nodes and links. In such a way, it is possible toaccurately make the time taken for voice guiding under a predeterminedreference value.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040]FIG. 1 is a block diagram showing a first convention navigationdevice.

[0041]FIG. 2 is a block diagram showing a second convention navigationdevice.

[0042]FIG. 3 is a flowchart explaining the operation of a secondconventional navigation device.

[0043]FIG. 4 is a block diagram showing a construction of a navigationdevice according to a first embodiment of the present invention.

[0044]FIG. 5 is a block diagram showing a construction of the hardwarein the navigation device shown in FIG. 4.

[0045]FIG. 6 shows an example of map information data stored in a mapinformation storage means.

[0046]FIG. 7 shows an example of a menu and a map displayed on a displaymeans.

[0047]FIG. 8 shows an example of a route determined by a route searchingmeans.

[0048]FIG. 9 shows an example of a menu for each setting category ofroute voice guides according to a first embodiment.

[0049]FIG. 10 is a flowchart of the operation of each section in routevoice guide processing.

[0050]FIG. 11 is a flowchart showing the details of the process ofextracting links and nodes as well as the proximate facilities to linksand nodes in step ST105 of FIG. 10.

[0051]FIG. 12 shows the relative relationship of guide number A anddistance X from a present position to a guide point obtained by thisformula.

[0052]FIG. 13 is a flowchart showing the details of the process ofgenerating a voice guide message for extracted links and nodes as wellas the proximate facilities to links and nodes in step ST106 of FIG. 10.

[0053]FIG. 14 is an example of a set of supplementary voice data.

[0054]FIG. 15 shows data related to extracted links and nodes as well asthe proximate facilities to links and nodes in the process shown in FIG.11 with respect to the route shown in FIG. 8.

[0055]FIG. 16 shows a voice guide message generated based on the datashown in FIG. 15.

[0056]FIG. 17 shows a display example of a menu for each category ofsetting of route voice guides according to a second embodiment.

[0057]FIG. 18 is a flowchart showing the details of the process ofextracting links and nodes as well as the proximate facilities to linksand nodes in a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] In order to describe the invention in greater detail, thepreferred embodiments will be outlined below with reference to theaccompanying figures.

[0059] Embodiment 1

[0060]FIG. 4 is a block diagram showing a construction of a navigationdevice according to a first embodiment of the present invention. FIG. 5is a block diagram showing a construction of the hardware in thenavigation device shown in FIG. 4.

[0061] In FIG. 4, reference numeral 21 denotes a control means whichexecutes each type of calculation in the navigation device and controlsother constitutive elements. 22 is a map information storage means whichpre-stores digitized map information data such as node data and linkdata displaying intersection points and roads. 23 is a present positiondetection means which detects a present position of a moving body inwhich the navigation device is mounted.

[0062]24 is a route search means which reads map information data storedin the map information storage means 22, which searches a route betweentwo geographic points in a map on the basis of map information data forexample on the basis of a Dijkstra method and which determines a singleroute. 25 is a route storage means which stores a route determined bythe route search means 24.

[0063]26 is a display means which displays a route and the like storedin the route storage means 25 and a map based on map information datastored in the map information storage means 22.

[0064]27 is a voice guide message generation means which has a voiceinformation storage means 31 which pre-stores voice waveform data suchas words and phrases required for voice guide messages. Voice waveformdata such as words and phrases constituting voice guide messages areselected when performing voice guiding and voice guide messages aregenerated by combining selected voice waveform data. 28 is a voiceoutput means which outputs voice corresponding to voice guide messagesgenerated by the voice guide message generated means 27 and whichreports the guide message to a user.

[0065]29 is an operation means which is operated when commands are inputinto the navigation device by user and which supplies an input usercommands to the control means 21. 30 is a voice guide informationextraction means which extracts main guide information from guideinformation on a route stored in the route storage means 25.

[0066] In FIG. 5, 51 is a CD-ROM storing digitized map information and aread-out device thereof which correspond to the map information storagemeans 22 shown in FIG. 4.

[0067]52 is a GPS receiver which receives electromagnetic waves from anartificial satellite using a geo-positioning system (GPS) and whichoutputs a present position of the moving body in which a navigationdevice is mounted. 53 is a bearing sensor which detects a bearing inwhich the moving body is directed. 54 is a distance sensor which detectsa movement distance of the moving body. These components correspond tothe present position detection means 23 shown in FIG. 4.

[0068]55 is a display device which has for example a liquid crystaldisplay and which displays map information, maps based on mapinformation data, determined routes and the like. The display devicecorresponds to the display means 26 shown in FIG. 4. 56 is a voiceoutput means which outputs voice guide messages. It corresponds to thevoice output means shown in FIG. 4. 57 is an input device which has aswitch operated when commands are input into the navigation device by auser and which supplies input user commands to a control unit 58. Theinput device 57 corresponds to the operation means shown in FIG. 4.

[0069]58 is a control unit provided with a central processing unit (CPU)61, a read only memory (ROM) 62, a random access memory (RAM) 63, adisplay control section 64 and an input/output control section 65. Thecontrol unit 58 calculates each type of calculation in the navigationdevice and executes control of other constitutive components. Thecontrol unit corresponds to the control means 21, the route search means24, the route storage means 25, the voice guide message generation means27 and the voice guide information extraction means 30 shown in FIG. 4.

[0070] In the control unit 58, 61 is a CPU which executes processing ofroute searching and guide point extraction. 62 is a ROM which pre-storesdata, programs and the like used by the CPU 61. 63 is a RAM into whichmap information data and programs used by the CPU 61 are loaded andwhich stores the calculation results of the CPU 61. 64 is a displaycontrol section which controls the display device 55 and which displayseach type of image on the display device 55. 65 is an input/outputcontrol section which executes transfer of signals and each type of databy acting as an interface between the control unit 58 and each type ofexternal device (CD-ROM and read-out device 51 to input device 57).

[0071]FIG. 6 shows an example of map information data stored in the mapinformation storage means 22.

[0072] The map information data comprises a node data group 110 beingthe set of data related to nodes and a link data group 130 being the setof data related to links.

[0073] The node data group 110 is comprised by a node data record 120which comprises each type of data related to each node. Each node datarecord 120 has a node number 121 which shows a distinguishing numberwhich is uniquely assigned to a node which corresponds to the node datarecord 120, a node coordinate 122 which shows latitude and longitude ofa position of a node on the map, a connecting link number 123 whichshows the number of links connecting the node, a link number 124 of eachlink connected to the node, a node name 125 which is the name of thenode, and a proximate facility data record 150 which is the set of datarelated to the proximate facilities which exist in the periphery of thenode. A node voice guide level 126 which shows a level of importance ofthe referred node when performing voice guiding of a route containingthe node and a node voice guide time 127 which shows a voice playingtime required for voice guiding of the node are also provided.

[0074] The proximate facility data record 150 has a facility name 151which shows the name of facilities in the environs of each node, afacility number 152 which displays a distinguishing number which isuniquely assigned to each facility, and a facility position 153 whichshows the position of the facility which corresponds to the node. Afacility voice guide level 154 which shows a level of importance of thereferred facility when performing voice guiding of a route containing anode and a facility voice guide time 155 which shows a voice dataplaying time required for voice guiding of the facility are alsoprovided.

[0075] The link data group 130 is comprised by link data record 140which comprises each type of data related to each link. Furthermore eachlink data record 140 comprises a link number 141 which shows adistinguishing number which is uniquely assigned to a link whichcorresponds to link data records 140, an start node number 142 whichshows a node connected to an start side of a link, a finish node number143 which shows a node connected to a finish side of a link a linklength 144 which shows the length of a link, and a link attribute datarecord 160 which is the set of each type of data related to a linkattribute.

[0076] The link attribute data record 160 has a link category 161, aflow regulation information 162 which shows flow regulation of a roadwhich corresponds to the link, a link name 163 which shows a name of alink, a link name number 164 which shows a distinguishing number whichis uniquely assigned to the name of a link, a link voice guide levelwhich shows the importance of a link referred to when performing voiceguiding of a route containing the link, and a link voice guide time 166which shows a voice data playing time required for voice guiding of thelink. Furthermore, a link proximate facility data record 170 is providedwhich is a set of data related to facilities in the proximity of thelink.

[0077] The link proximate facility data record 170 comprises a facilityname 171 which shows a facility name, a facility number 172 which showsa distinguishing number which is uniquely assigned to the facility, afacility position 173 which shows a position of facilities with respectto the link, and a facility voice guide level 174 which shows theimportance of a facility referred to when performing voice guiding of aroute containing a link, and a facility voice guide time 175 which showsa voice data playing time required for voice guiding of the facility.

[0078] The level of importance shown by the facility voice guide level174 can be determined by consideration of the level of reputation of thefacility in the general community or with reference to a standarddetermined nationally. Alternatively they may be determined by any otherstandard.

[0079] On such a way, a node voice guide level 126 which shows a levelof importance of each individual node and a corresponding node voicelevel guide time 127 which shows the time required for voice guiding thenode, as well as a facility voice guide level 154 which shows a level ofimportance of each individual facility and a facility voice level guidetime 155 which shows the time required for voice guiding the facilityare contained in the map information data. Furthermore, a link voiceguide level 165 which shows a level of importance of each individuallink and a link voice level guide time 166 which shows the time requiredfor voice guiding the link, as well as a facility voice guide level 174which shows a level of importance of each individual facility and afacility voice level guide time 175 which shows the time required forvoice guiding the facility are contained in the map information data.

[0080] The operation of the present invention will be described below.

[0081] The control means 21 displays a map corresponding to the mapinformation data in the display means 26 in response to an operation ofa user. A menu or the like is displayed for selecting each function.FIG. 7 shows an example of a menu and a map displayed on the displaymeans 26. In the figure, a moving body mark 211 which shows the presentposition of the moving body, a bearing mark 212 which shows thedirection of the map, a route line 213 which shows a route determined bythe route search process to be discussed below and a menu 214 forselecting each function such as setting a destination are displayed onthe map. When making a selection on the menu, a cursor is moved inresponse to an operation of a user on the operation means 29 and aselection is made.

[0082] When a destination is selected, firstly the route search processis performed. At this time, the present position detected by the presentposition detection means 23 and the destination input to the operationmeans 29 by a user are supplied to the route search means 24 by thecontrol means 21. Map information data is read from the map informationstorage means 22 by the route search means 24, routes between thepresent position and the destination are searched by a Dijkstra methodfor example and a single route is determined. Information relating tonodes and links which comprise the route are stored in the route storagemeans 25.

[0083]FIG. 8 is an example of a route determined by the route searchmeans 24. On the route shown in FIG. 8, there are 15 nodes N001-N00Fbetween a present position and a destination (the figures arehexadecimal numbers). There are 14 (=15-1) links L000-L00D (the figuresare hexadecimal numbers) connecting each node.

[0084] Since route voice guiding becomes possible when a route isdiscovered by the route search process, options (route outline)corresponding to the function of route voice guide on the menu as shownin FIG. 7 are varied to be selectable by an operation of the user. Thatis to say, before execution of the route search process or when no routeis found, it is not possible for the user to make a selection and theoption “route outline” is covered (i.e. displayed gray).

[0085] Each category of setting the route voice guide is executed beforeroute voice guide processing. First the control means 21 displays a menufor each setting type of the route voice guide on the display means 26.FIG. 9 shows an example of a menu display for each type of setting ofthe route voice guide according to a first embodiment. In the menu inFIG. 9, there is a guide point selection term 201 which sets theexecution of the route voice guide from a present position to anygeographical point, a guide number selection term 202 which sets thetotal (guide number) of proximate facilities of a link or node as wellas links and nodes which execute the voice guiding of the routes from apresent position to a destination and a guide level selection term 203which sets the level of detail of the voice guide.

[0086] There are the options “destination” and “detour” in the guidegeographical point selection term 201. The selection of the option isexecuted by a user operating the operation means 29. When “destination”is selected, route voice guide from a present position to a destinationis performed. When “route” is selected, route voice guide from a presentposition to a predetermined detour point is performed. Although there isone option “detour” in the guide geographical point selection term 201in FIG. 9, the option may be adapted to provide a plurality of detoursas options or to add an option “selectable geographical point” for theuser to select a final geographical point for voice guiding in thedisplayed map.

[0087] The guide number selection term has the options “5”, “10”, “20”and “automatic”. The selection of these options is performed by theoperation of the operational means 29 by the user. When any of “5”, “10”or “20” are selected, a respectively corresponding number (5, 10, 20) isset as the total number of proximate facilities for a link or node or asa link or node which executes the voice guide. When “automatic” is set,a guide number (discussed below) which is calculated in response to thedistance from a present position to a guide point is set as the totalnumber of proximate facilities for a link or node or as a link or nodewhich executes the voice guide. When setting the guide number of aguided node or the like, apart from selecting a predetermined number asabove, the device is adapted to allow a user to directly set a value asa guide number.

[0088] The guide level selection term 203 has the options “high”,“medium” and “low”. The selection of these options is executed by a useroperating the operation means 29. When “high” is selected, voice guidingis performed to nodes, links and facilities proximate to nodes and linksof low importance as far as allowed by the guide number above. When“low” is selected, voice guiding is performed only to nodes, links andfacilities proximate to nodes and links of high importance as far asallowed by the guide number above. When “medium” is selected, voiceguiding is performed only to nodes, links and facilities proximate tonodes and links of medium importance as far as allowed by the guidenumber above. The setting of the reference value for level of importancewhen selecting a guided node, apart from selecting a predetermined levelas above may be performed by the user directly setting a level ofimportance with a value.

[0089] Thus, a reference number setting means and a reference valuesetting means which set a guide level and guide number are comprised byan operational means 29 and a display means 26 on which a menu isdisplayed.

[0090] Next, route voice guide processing is performed. FIG. 10 is aflowchart of the operation of each section in route voice guideprocessing. Firstly, as a result of the route search process beingexecuted, the routine progresses from step ST101 to step ST102 when theroute is determined. Thus, the gray cover on the menu option “routeoutline” is withdrawn allowing this option to be selected. When theoption “route outline” is selected, route voice guide processing isperformed (step ST103).

[0091] Firstly, in a step ST104, a present position of the moving bodyis detected by the present position detection means 23. Then, in a stepST105, the voice guide information extraction means 30 reads datarelating to nodes and links which comprise the determined route andextracts a number of nodes, links and proximate facilities to nodes andlinks of high importance corresponding to the guide number above basedon voice guide information extraction conditions set by the user in themenu (FIG. 9).

[0092] Then, in a step ST106, the extracted nodes and links andproximate facilities to nodes and links are supplied to the voice guidemessage generation means through the control means 21. The voice guidemessage generation means 27 generates voice guide messages relating tothe extracted nodes and links and proximate facilities to nodes andlinks. When a voice guide message is generated, it is supplied to thevoice output means 28 by the control means 21. In a step ST107, thevoice guide message is output by the voice output means 28 and anoutline of the route from a present position to a guide point isreported to a user.

[0093] By adapting the output of voice guide messages in this way, anoutline of a searched route may be guided.

[0094] Next, in the above step ST105, the details of the process ofextracting nodes and links and proximate facilities to nodes and linkswill be described. FIG. 11 is a flowchart of the details of the processof extracting nodes and links and proximate facilities to nodes andlinks in step ST105 in FIG. 10.

[0095] Firstly, in a step ST121, the voice guide information extractionmeans 30 reads information relating to guide level terms, guide numberterms and guide point terms set by the user from the control means 21,stores the node number of selected geographical points based oninformation about the guide point term and stores an extracted guidenumber Abased on information about the guide number term. When“automatic” is selected at this time, the guide number A is stored as 0.The voice guide information extraction means 30 stores a value 100 as areference value GL when the guide level “high” is selected based on theinformation of the guide level term. When the selected guide level is“medium”, the value 10 is stored as the reference level GL, and when theselected guide level is “low”, the value 5 is stored as the referencelevel GL.

[0096] The voice guide information extraction means 30 sets the initiallevel of the extraction level L of the importance of extracted nodes,links and proximate facilities to 0. (In FIG. 6 these are shown as thefacility voice guide level 154, 174, the link voice guide level 165, andthe node voice guide level 126). When the extraction level L is 0,proximate facilities and nodes and links which are less than or equal toan extracted level of 0 are extracted and as discussed below, the valueof the extraction level L is incremented sequentially by values of 1.Thus, only more important information is extracted as the value of theextraction level L reduces.

[0097] In the next step ST122, the voice guide information extractionmeans 30 determines whether or not the guide number A is 0. That is tosay, it is determined whether or not “automatic” has been selected as aguide number term.

[0098] The voice guide information extraction means 30 reads linkinformation comprising route determined in the step ST123 from the mapinformation storage means 22 when the guide number A is 0. A route X(kilometers) is calculated from the present position to the guide point(the destination or detour) on the basis of the link information. Instep ST124, the guide number A is calculated on the basis of thefollowing formula.

A∴INT(Log (X+1)^(0.7)×6+0.5)

[0099] The term INT(y) is a function which outputs an integer which is areal number (y) in which decimal points are rounded off. FIG. 12 showsthe corresponding relationship of a guide number A and the distance Xfrom a present position to a guide point obtained by the formula. Asshown in FIG. 12, the increment of the guide number A decreases as thedistance X increases. In embodiment 1, the guide number A which is setto “automatic” is calculated by the above formula. However, thecalculation may be performed on the basis of another formula withdistance or other element as a variable. When the guide number A is notequal to 0, the processes in steps ST123 and ST124 are not performed.

[0100] In the step ST125, the voice guide information extraction means30 sets the extraction number SS (L) which shows the total of proximatefacilities and nodes and links with an importance of less than theextraction level L, to an initial value of 0.

[0101] Then, in a step ST126, the voice guide information extractionmeans 30 selects and extracts the node voice guide level 126, the linkvoice guide level 165 and the facility voice guide level 153, 174 asshown in FIG. 6 from the nodes, links and proximate facilities from thepresent position to the guide point based on information regarding nodesand links which comprise the route which is stored in the route storagememory 25. That is to say, nodes, links and proximate facilities areselected and extracted which have the same level of importance as theextraction level L.

[0102] After the nodes, links and proximate facilities which have thesame level of importance as the extraction level L are extracted, in astep ST127, the voice guide information extraction means 30 selectslinks from the extracted links and makes two adjacent links with thesame link name number into one link. When the two links are varied intoone link in this fashion, the link number, the start intersection numberand the link attribute of the link after variation are assigned fromthat link of the two original links which is nearer the presentposition. The finish intersection number is assigned from that link ofthe two original links which is near the guide point. The link length ofthe link after variation is equal to the sum of the respective lengthsof the two original links. Furthermore data relating to proximatefacility links of links after variation contains data relating toproximate facility links of the two original links. Thus, the facilityposition of each proximate facility is calculated and set to a positioncorresponding to links after variation.

[0103] In a step ST128, the voice guide information extraction means 30updates the extraction number SS (L) by the sum of the number S(L) ofextracted nodes, links and related proximate facilities in current stepST126 and the extraction number SS(L-1) when the extraction level L isonly smaller by a value of 1.

[0104] After the extraction number SS(L) in the extraction level L atthis time is calculated, in a step ST129, the voice guide informationextraction means 30 determines whether or not the extraction numberSS(L) is greater than or equal to the guide number A above. When theextraction number SS(L) is not greater than or equal to the guide numberA, in a step ST130, the voice guide information extraction means 30determines whether the extraction level L is smaller than a referencevalue GL of the guide level above. When the extraction level L issmaller than the reference level GL of the guide level above, in a stepST131, the value of the extraction level L is increased by 1 and theroutine returns to the step ST126. Thus, the extraction of the nodes,links and related proximate facilities corresponding to this extractionlevel L are executed in the same way. On the other hand, in a stepST130. when the extracted level L is smaller than the reference value GLof the guide level above, it is determined whether all the nodes, links,and related proximate facilities with a level of importance up to theset reference value GL have been extracted or not and the process ofstep ST105 is completed.

[0105] In the step ST129, when the extracted level SS(L) is greater thanthe guide number A, in step ST132, the voice guide informationextraction means 30 determines whether or not the extraction numberSS(L) is the same as the guide number A. When the two are the same, itis determined that a number of nodes, links and proximate facilities ofequal to the set guide number A has been extracted and the processing ofstep ST105 is completed.

[0106] In the step ST132, when the extraction number SS(L) is not thesame as the guide number A, that is to say, when the extraction numberSS is greater than the guide number A, the voice guide informationextraction means 30 deletes one of the nodes, links or related proximatefacilities by the following process until the extraction number SS(L)equals the guide number A.

[0107] Firstly, in a step ST133, the voice guide information extractionmeans 30 determines that the number of proximate facilities with anextracted level of importance L is greater than the difference (SS(L)-A)of the extraction number SS(L) and the guide number A. The voice guideinformation extraction means 30 also determines whether it is possibleto delete related proximate facilities from the environs of the guidepoint until the extraction number SS(L) and the guide number A have thesame value. When it is determined that it is possible to delete relatedproximate facilities from the environs of the guide point until theextraction number SS(L) and the guide number A have the same value, theproximate facilities are deleted in a step ST134 and the extractionnumber SS(L) is made equal to the guide number A.

[0108] When the number of proximate facilities with an extractionimportance of L is less than the difference (SS(L)-A) of the extractionnumber SS(L) and the guide number A, in a step ST135, the voice guideinformation extraction means 30 deletes all the proximate facilitiesfrom the extracted nodes, links and related proximate facilities andupdates the extraction number SS(L) by subtracting that number ofproximate facilities.

[0109] Thereafter, in a step ST136, the voice guide informationextraction means 30 determines whether the number of nodes from amongextracted nodes with an importance of L to which extracted links with animportance of L are not connected is greater than the difference(SS(L)-A) of the extraction number SS(L) and the guide number A. Thevoice guide information extraction means 30 also determines whether itis possible to delete such nodes from the environs of the guide pointuntil the extraction number SS(L) and the guide number A have the samevalue. When it is determined that it is possible to delete nodes fromthe environs of the guide point until the extraction number SS(L) andthe guide number A have the same value, the nodes are deleted in a stepST137 and the extraction number SS(L) is made equal to the guide numberA.

[0110] When the number of nodes to which extracted links with animportance of L are not connected is less than the difference (SS(L)-A)of the extraction number SS(L) and the guide number A, in a step ST138,the voice guide information extraction means 30 deletes all nodes towhich extracted links with an importance of L are not connected from theextracted nodes, links and related proximate facilities and updates theextraction number SS(L) by subtracting that number of nodes.

[0111] Thereafter, in a step ST139, the voice guide informationextraction means 30 determines whether the number of remaining extractednodes with an importance of L is greater than the difference (SS(L)-A)of the extraction number SS(L) and the guide number A. The voice guideinformation extraction means 30 also determines whether it is possibleto delete such nodes from the environs of the guide point until theextraction number SS(L) and the guide number A have the same value. Whenit is determined that it is possible to delete nodes from the environsof the guide point until the extraction number SS(L) and the guidenumber A have the same value, the nodes are deleted in a step ST140 andthe extraction number SS(L) is made equal to the guide number A.

[0112] When the number of remaining extracted nodes with an importanceof L is less than the difference (SS(L)-A) of the extraction numberSS(L) and the guide number A, in a step ST141, the voice guideinformation extraction means 30 deletes all remaining extracted nodeswith an importance of L from the extracted nodes, links and relatedproximate facilities and updates the extraction number SS(L) bysubtracting that number of nodes.

[0113] Thereafter, in a step ST142, the voice guide informationextraction means 30 determines whether the number of links to whichextracted nodes with an importance of L are not connected is greaterthan the difference (SS(L)-A) of the extraction number SS(L) and theguide number A. The voice guide information extraction means 30 alsodetermines whether it is possible to delete such links from the environsof the guide point until the extraction number SS(L) and the guidenumber A have the same value. When it is determined that it is possibleto delete such links from the environs of the guide point until theextraction number SS(L) and the guide number A have the same value, thelinks are deleted in a step ST 143 and the extraction number SS(L) ismade equal to the guide number A.

[0114] When the number of links to which extracted nodes with animportance of L are not connected is less than the difference (SS(L)-A)of the extraction number SS(L) and the guide number A, in a step ST144,the voice guide information extraction means 30 deletes all such linksfrom the extracted nodes, links and related proximate facilities andupdates the extraction number SS(L) by subtracting the total number ofnodes.

[0115] Thereafter, in a step ST145, the voice guide informationextraction means 30 deletes links near to the guide point from theremaining extracted links which have an importance of L and thus makesthe extraction number SS(L) equal to the guide number A.

[0116] In such a way, nodes and the like are extracted in order ofimportance and when the extraction number SS(L) is greater than theguide number A, nodes and the like are deleted from near the guide pointuntil the same number of nodes or the like as the guide point A near thepresent position is selected. After the extraction number SS(L) and theguide number A are made equal, the process of step ST105 is completed.

[0117] The process of generating a voice guide message regardingextracted links, nodes and proximate facilities of links or nodes in astep ST106 will be described below. FIG. 13 is a flowchart showing thedetails of the process of generating a voice guide message for extractedlinks and nodes as well as the proximate facilities of links and nodesin step ST106 of FIG. 10.

[0118] After extracted links and nodes as well as the proximatefacilities to links and nodes are supplied to the voice guide messagegenerating means 27 through the control means 27, in a step 151, thevoice guide message generating means 27 firstly output data relating toextracted links and nodes as well as the proximate facilities to linksand nodes in order of data proximate to a present position. At thistime, the data relating to node proximate facilities is stated with thenode proximate facility closer to the present position than the node.The data relating to link proximate facilities is stated with the linkproximate facility further from the present position than the link.

[0119] The voice guide message generation means 27 adds a group flag GFto data related to nodes, links and related proximate facilitiescomprising the route. Thereafter a value of 1 is assigned to the groupflag GF of the mutually connected nodes and links, to nodes and relatedproximate facilities to that node, or to nodes, links and proximatefacilities related to links and proximate facilities to that link.However, the group flag GF of data which is closest to the guide pointin the group is set to a value of 0.

[0120] Next, in a step ST152, the voice guide message generation means27 extracts voice waveform data corresponding to extracted nodes, linksand proximate facilities related to nodes and links from the storedvoice information storage means 31. Such voice waveform data consists ofthe names of nodes, names of links, or the names of proximate facilitiesrelated to nodes and links.

[0121] In a step ST153, the voice guide message generation means 27takes out supplementary voice data corresponding to predicates from thevoice information storage means 31 and generates a voice guide messagecontaining the previously taken out voice waveform data for each name.

[0122]FIG. 14 shows an example of a set of supplementary voice data.When the supplementary voice data shown in FIG. 14 is pre-stored in thevoice information storage means 31, a voice guide message is generatedby one of the following procedures by adding supplementary voice data toeach name of nodes or the like in the stated order of step ST151 andthen stating the data sequentially.

[0123] Procedure 1.

[0124] When a right turn is made on the route at a node, supplementaryvoice data (make right turn.) of distinguishing number 301 is addedafter the voice waveform data of the node name when the group flag GFhas a value of 0. When the group flag GF has a value of 1, supplementaryvoice data (make right turn and . . . ) of distinguishing number 401 isadded.

[0125] Procedure 2.

[0126] When a left turn is made on the route at a node, supplementaryvoice data (make left turn.) of distinguishing number 302 is added afterthe voice waveform data of the node name when the group flag GF has avalue of 0. When the group flag GF has a value of 1, supplementary voicedata (make left turn and.. ) of distinguishing number 402 is added.

[0127] Procedure 3.

[0128] When a vehicle continues traveling in the same direction on theroute at a node, supplementary voice data (continue straight.) ofdistinguishing number 303 is added after the voice waveform data of thenode name when the group flag GF has a value of 0. When the group flagGF has a value of 1, supplementary voice data (continue straight and . .. ) of distinguishing number 403 is added.

[0129] Procedure 4.

[0130] When a vehicle makes a U-turn on the route at a node,supplementary voice data (make a U-turn) of distinguishing number 304 isadded after the voice waveform data of the node name when the group flagGF has a value of 0. When the group flag GF has a value of 1,supplementary voice data (make a U-turn and) of distinguishing number404 is added.

[0131] Procedure 5.

[0132] When a vehicle continues traveling in the same direction on theroute at a link, supplementary voice data (continue straight.) ofdistinguishing number 303 is added after the voice waveform data of thelink name when the group flag GF has a value of 0. When the group flagGF has a value of 1, supplementary voice data (continue straight and . .. ) of distinguishing number 403 is added.

[0133] Procedure 6.

[0134] When a link is a bridge, supplementary voice data ( . . . cross.)of distinguishing number 305 is added after the voice waveform data ofthe link name when the group flag GF has a value of 0. When the groupflag GF has a value of 1, supplementary voice data (. . . cross and . .. ) of distinguishing number 405 is added.

[0135] Procedure 7.

[0136] When a node is an entrance to an expressway, supplementary voicedata (enter . . . ) of distinguishing number 306 is added after thevoice waveform data of the node name when the group flag GF has a valueof 0. When the group flag GF has a value of 1, supplementary voice data(enter and . . . ) of distinguishing number 406 is added.

[0137] Procedure 8.

[0138] When a node is an exit of an expressway, supplementary voice data(exit...) of distinguishing number 307 is added after the voice waveformdata of the node name when the group flag GF has a value of 0. When thegroup flag GF has a value of 1, supplementary voice data (exit . . . and. . . ) of distinguishing number 407 is added.

[0139] Procedure 9.

[0140] When the group flag GF has a value of 0 at a link proximatefacility, supplementary voice data (pass on the... side) ofdistinguishing number 308 is added after the voice waveform data of thelink proximate facility name. When the group flag GF has a value of 1,supplementary voice data (pass on the . . . side and . . . ) ofdistinguishing number 408 is added.

[0141] Procedure 10.

[0142] When the group flag GF has a value of 0, the route turns to theright at a node which is a node proximate facility, supplementary voicedata (turn right at the mark) of distinguishing number 309 is addedafter the voice waveform data of the node proximate facility name. Whenthe group flag GF has a value of 1, supplementary voice data (at themark . . . ) of distinguishing number 409 is added.

[0143] Procedure 11.

[0144] When the group flag GF has a value of 0, the route turns to theleft at a node which is a node proximate facility and supplementaryvoice data (turn left at the mark) of distinguishing number 310 is addedafter the voice waveform data of the node proximate facility name. Whenthe group flag GF has a value of 1, supplementary voice data (at themark . . . ) of distinguishing number 409 is added.

[0145] Procedure 12.

[0146] When the group flag GF has a value of 0, the route continues inthe same direction at a node which is a node proximate facility andsupplementary voice data (continue straight at the mark) ofdistinguishing number 311 is added after the voice waveform data of thenode proximate facility name. When the group flag GF has a value of 1,supplementary voice data (continue straight at the mark) ofdistinguishing number 409 is added.

[0147] The route search means 24 predetermines whether the route turnsleft or right or continues straight at each node or whether a link is abridge.

[0148]FIG. 15 shows data related to extracted nodes, links and proximatefacilities of nodes and links through a process shown in FIG. 11 withrespect to the route shows in FIG. 8. FIG. 16 shows a voice guidemessage generated based on data shown in FIG. 15. The link L001 shown inFIG. 15 is a single link made up of links L001, L002, L003 in FIG. 8 bythe process of step ST127 shown in FIG. 11. In the same way, the linkL005 shown in FIG. 15 is a single link made up of links L005, L006, L007in FIG. 8. The link proximate facility S251 (not shown) belongs to thelink L002 in FIG. 8, however it is varied to belong to the link L001after variation by the process of step ST127.

[0149] In the step ST151 as shown in FIG. 13, the link L001, the linkproximate facility S251 and the node N005 is made into a group 500 andthe node N006, the link L005 and the node N009 are made into the group501. A voice guide message shown in FIG. 16 is generated by steps ST152,ST153 in FIG. 13 with respect to extracted nodes, links and proximatefacilities to nodes and links.

[0150] In such a way, a voice guide message is generated and output tothe voice output means 28.

[0151] As shown above, according to embodiment 1, the importance ofnodes and links is stored. Nodes and links are selected from amongstnodes and links on a searched route based on their importance. Voiceguide messages are generated with respect to selected nodes and linksand such messages are used to execute guiding of a route by voicecommands. Thus, it is possible to guide an entire route appropriately ina short time by voice.

[0152] Furthermore, when a plurality of nodes and links which have equalimportance exist and their number does not equal a predeterminedreference number, a number of nodes which equals the predeterminedreference number is selected from those nodes of equal importance nearto a present position. Thus, it is possible to accurately correspond thenumber of guided nodes or the like with a predetermined referencenumber.

[0153] Embodiment 2

[0154] The navigation device according to embodiment 2 of the presentinvention summarizes nodes, links and related proximate facilities onthe route which are voiced guided based on a guide time pre-set by auser instead of summarizing on the basis of the level of importance andpredetermined guide number of nodes, links and related proximatefacilities on the voiced-guided route. That is to say, this is avariation on the process (FIG. 11) of step ST105 in FIG. 10 of thenavigation device according to the first embodiment.

[0155] Thus, according to embodiment 2, the summarizing process entailssummarizing nodes, links and related proximate facilities on thevoiced-guided route. In other respects, the present embodiment is thesame as the first embodiment and such description will be omitted.

[0156] Before the route voice guide process, all types of settingsrelated to the route voice guiding are executed. Firstly, the controlmeans 21 displays a menu on the display means 26 for all types ofsettings for route voice guiding. FIG. 17 shows a display example of amenu for displaying each type of setting for route voice guidingaccording to embodiment 2.

[0157] The menu shown in FIG. 17 comprises a guide point selection term601 which sets the execution of route voice guiding from a presentposition to a given geographical point and a guide time selection term602 which sets a guide time for voice guiding of the route from apresent position to a guide point.

[0158] The guide point selection term 601 contains the options“destination” and “detour”. The selection of the options is executed bya user operating the operational means 29. When “destination” isselected, route voice guiding from a present position to a destinationis executed. When “detour” is set, route voice guiding from a presentposition to a predetermined detour point is executed. The guide pointselection term 601 in FIG. 17 has one option “detour”. However, aplurality of detours may be selected as options or the user may add“selectable geographic points” as options to select a final geographicpoint for voice guiding.

[0159] The guide time selection term 602 has the options “short”,“middle” and “long”. The selection of these options is executed by auser operating the operational means 29. When “short” is selected by auser with respect to nodes, links and related proximate facilities on aroute, voice guiding is performed for approximately 15 sec. When“middle” is selected, voice guiding is performed for approximately 30sec. When “long” is selected, voice guiding is performed forapproximately 1 minute. The user may directly select a time limit forvoice guiding with a figure.

[0160] Now the extraction process of nodes, links and related proximatefacilities according to embodiment 2 will be described. FIG. 18 is aflowchart showing the details of the process of extracting links andnodes as well as the proximate facilities of links and nodes in a secondembodiment.

[0161] Firstly, in a step ST201, the voice guiding informationextraction means 30 reads information relating to guide time terms andguide point terms set by a user from the control means 21. The nodenumber of the selected geographical point is stored based on informationrelating to the guide point term. A selected guide time is set to areference value B for guide times based on information relating to theguide time term. The voice guide information extraction means 30 set anextraction level L which shows the importance of extracted nodes, linksand related proximate facilities (in FIG. 6, a node voice guiding level126, a link voice guiding level 165 and a facility voice guiding level154, 174) to a value of 0. When the extraction level L is 0, the nodes,links and related facilities with an extraction level of equal to orless than 0 are extracted. As described below, the value of theextraction level L is sequentially incremented by values of 1. Thus,only increasingly important information is extracted at lower extractionlevel values L.

[0162] In a step ST202, a voice guiding information extraction means 30sets an initial value 0 to an extraction number SS(L) which shows thetotal number of nodes, links and related facilities with an importanceequal to or less than an extraction level of L. An initial value 0 isset to a total guide time ST(L) which is required to voice guide nodes,links and related facilities with a level of importance less than orequal to an extraction level L.

[0163] Then, in the step ST203, the voice guiding information extractionmeans 30 selects and extracts node voice guiding level 126, link voiceguiding level 165 and facility voice guiding level 154, 174 shown inFIG. 6, that is to say, nodes, links and related facilities which havean equal extraction level L of importance from amongst the nodes, linksand related proximate facilities from a present point to a guide pointbased on node and link information comprising a route stored in theroute storage means 25.

[0164] After selecting and extracting nodes, links and relatedfacilities which have an equal extraction level L of importance, in astep ST204, of the extracted links, the voice guiding informationextraction means 30 converts two adjacent links with the same link namenumber into one link. When two such links are converted into one link,the link number of the link after conversion, the start intersectionnumber and the link attribute are assigned from the link of the twooriginal links which is nearer to the present position. The finishintersection point number is assigned from the link of the two originallinks which is nearer to the guide point. The link length of the linkafter conversion is the sum of the link lengths of the two originallinks. With respect to data about the link proximate facilities of thelink after conversion, data is stored with respect to the proximatefacilities of the two original links and facility positions for eachtype of proximate facility is calculated and set to a position whichcorresponds to the link after conversion.

[0165] In step ST205, the voice guiding information extraction means 30updates the extraction number SS(L) by the sum of the number S(L) ofextracted nodes, links and related proximate facilities in the currentstep ST203 and the extraction number SS(L-1) in which the extractionlevel L is smaller by a value of 1. Further it updates the total guidingtime ST(L) by the sum of the number T(L) of guiding time required forextracted nodes, links and related proximate facilities in the currentstep ST203 and the total guiding time ST(L-1) in which the extractionlevel L is smaller by a value of 1. The sum T(L) of guiding timerequired for extracted nodes, links and related proximate facilities isthe total of the node voice guiding time 127, the facility voice guidingtime 155, the link voice guiding time 166 and the facility voice guidingtime 175 in the map information data shown in FIG. 6.

[0166] After the calculation of the extraction number SS(L) and thetotal guiding time ST(L) in the extraction level L at that point intime, in a step ST206, the voice guiding information extraction means 30determines whether or not twice the sum of the total guiding time ST(L)and the extraction number SS(L): (ST(L)+SS(L) x 2) is less than or equalto the reference value B above.

[0167] The comparison of twice the sum of the total guiding time ST(L)and the extraction number SS(L): (ST(L)+SS(L) x 2) with the referencevalue B above is performed for the following reason. The total guidetime ST(L) is the total sum of voice playing times for names such asextracted nodes. In addition, the voice playing time required forsupplementary voice data referred to above which is added to each nodeis on average two seconds. The playing time for voice guide messages upto an extraction level 1 at that time thus becomes (ST(L)+SS(L) x 2).Thus, when other supplementary voice data is used, (ST(L)+SS(L) x Ts) iscompared with a reference value B based on an average playing time Tsfor supplementary voice data in response to the length of thesupplementary voice data.

[0168] When the voice guide message playing time to an extraction levelL (ST(L)+SS(L) x 2) is not greater than or equal to the reference valueB, after the value of the extraction level L is increased by a value of1 in a step ST207, the routine returns to step ST203 and the extractionof nodes, links and related proximate facilities which correspond to anextraction level L is executed in the same way.

[0169] On the other hand, when the voice guide message playing time toan extraction level L is greater than or equal to a reference level B,in a step ST208, the voice guiding information extraction means 30determines whether or not the voice guide message playing time to anextraction level L is the same as the reference level B. When both arethe same, it is determined that the nodes, links and related proximatefacilities in a set guide time have been extracted and the routine iscompleted.

[0170] When the voice guide message playing time to an extraction levelL is not the same as a reference level B, that is to say, the voiceguide message playing time to an extraction level L (ST(L)+SS(L) x 2) isgreater than a reference level B, the voice guiding informationextraction means 30 deletes by the following process any of the nodes,links and related facilities with a level of importance L until thevoice guide message playing time to an extraction level L (ST(L)+SS(L) x2) is less than or equal to a reference level B.

[0171] Firstly, in a step ST209, the voice guiding informationextraction means 30 determines that the sum of the facility voiceguiding time for proximate facilities with an extracted importance of Lis greater than the difference of the voice guide message playing timeto an extraction level L (ST(L)+SS(L) x 2) and a reference level B.Then, it is determined whether or not it is possible to delete fromthose proximate facilities which are near to guide points until thevoice guide message playing time is less than or equal to the referencevalue B. When it is determined that it is possible to delete from thoseproximate facilities which are near to guide points until the voiceguide message playing time is less than or equal to the reference valueB, in a step ST210 such proximate facilities are deleted until the voiceguide message playing time is less than or equal to the reference valueB.

[0172] On the other hand, when it is determined that the sum of thefacility voice guiding time for proximate facilities with an extractedimportance of L is smaller than the difference of the voice guidemessage playing time to an extraction level L and the reference level B,in a step ST211, the voice guiding information extraction means 30deletes all proximate facilities from extracted nodes, links and relatedproximate facilities, reduces the total guide time ST(L) by the sum ofthe facility voice guide time for proximate facilities and updates thevalue. Also the value is updated by reducing the value of the extractionnumber SS(L) by the total number of proximate facilities.

[0173] Thereafter, in a step ST212, of the nodes which have an extractedimportance of L, the voice guiding information extraction means 30determines that the sum of the node voice guiding time for nodes with anextracted importance of L to which links are not connected is greaterthan the difference of the voice guide message playing time to anextraction level L and a reference level B. Then, it is determinedwhether or not it is possible to delete from those nodes which are nearto guide points until the voice guide message playing time is less thanor equal to the reference value B. When it is determined that it ispossible to delete from those nodes which are near to guide points untilthe voice guide message playing time is less than or equal to thereference value B, in a step ST213 such nodes are deleted until thevoice guide message playing time is less than or equal to the referencevalue B.

[0174] On the other hand, when it is determined that the sum of the nodevoice guiding time for nodes with an extracted importance of L notconnected to links is smaller than the difference of the voice guidemessage playing time to an extraction level L and the reference level B,in a step ST214, the voice guiding information extraction means 30deletes all nodes which have an extracted importance of L not connectedto links from extracted nodes, links and related proximate facilities,reduces the total guide time ST(L) by the sum of the node voice guidetime for such nodes and updates the value. Also the value is updated byreducing the value of the extraction number SS(L) by the total number ofnodes.

[0175] Thereafter, in a step ST215, the voice guiding informationextraction means 30 determines that the sum of the node voice guidingtime for remaining nodes which have an extracted importance of L isgreater than or equal to the difference of the voice guide messageplaying time to an extraction level L and a reference level B. Then, itis determined whether or not it is possible to delete from those nodeswhich are near to guide points until the voice guide message playingtime is less than or equal to the reference value B. When it isdetermined that it is possible to delete from those nodes which are nearto guide points until the voice guide message playing time is less thanor equal to the reference value B, in a step ST216 such nodes aredeleted until the voice guide message playing time is less than or equalto the reference value B.

[0176] On the other hand, when the sum of the node voice guiding timefor remaining nodes which have an extracted importance of L is smallerthan the difference of the voice guide message playing time to anextraction level L and a reference level B, the voice guidinginformation extraction means 30, in a step ST217, deletes all remainingnodes which have an extracted importance of L from the extracted nodes,links and related proximate facilities. The value for the total guidetime ST(L) is reduced by the sum of the node voice guiding times forsuch nodes and the value is updated. Also, the value for extractionnumber SS(L) is updated by being reduced by the total number of suchnodes.

[0177] Thereafter, in a step ST218, the voice guiding informationextraction means 30 determines that of links with an extractedimportance of L, the sum of the link voice guiding time for links withan extracted importance of L not connected to nodes is greater than thedifference of the voice guide message playing time to an extractionlevel L and a reference level B. Then, it is determined whether or notit is possible to delete from those links which are near to guide pointsuntil the voice guide message playing time is less than or equal to thereference value B. When it is determined that it is possible to deletelinks which are near to guide points until the voice guide messageplaying time is less than or equal to the reference value B, in a stepST219 such nodes are deleted until the voice guide message playing timeis less than or equal to the reference value B.

[0178] On the other hand, when the sum of the link voice guiding timefor links not connected to nodes which have an extracted importance of Lis smaller than the difference of the voice guide message playing timewith an extraction level L and a reference level B, the voice guidinginformation extraction means 30, in a step ST220, deletes all such linksfrom the extracted nodes, links and related proximate facilities. Thevalue for the total guide time ST(L) is reduced by the sum of the linkvoice guiding times for such links and the value is updated. Also, thevalue for extraction number SS(L) is updated by being reduced by thetotal number of such links.

[0179] Thereafter, in a step ST221, the voice guiding informationextraction means 30 deletes such links which are near to guide pointsfrom the remaining links with an extracted importance of L until thevoice guide message playing time is less than or equal to the referencevalue B.

[0180] In such a way, when nodes of high importance are extractedsequentially and a voice guide message playing time (ST(L)+SS(L) x 2) toan extraction level L is greater than or equal to a reference value B ofa guide time, a guide time is selected in a range of basic values forguide times by deleting nodes and the like in order of those near guidepoints. Thus, after the playing time of the voice guide message is lessthan or equal to a reference value for playing times, the routine iscompleted.

[0181] As shown above, according to embodiment 2, when there are aplurality of links and nodes with the same level of importance and whenplaying time of the voice guide message is greater than a predeterminedreference value, nodes or the like are selected from the nodes and linkswith the same level of importance from those near to a present positionso that the playing time of the voice guide message is less than apredetermined reference value. Thus, it is possible to make the time forvoice guiding to be accurately less than or equal to a predeterminedreference value.

[0182] The present invention is not limited to embodiments 1 and 2 aboveand may be applied through other embodiments. For example, theextraction method of guiding points may vary the node or link extractionconditions.

[0183] Furthermore, the voice-guide message generated by the voice guidemessage generation means 27 may generate messages which guide theposition of a facility, a time or a distance apart from the examplesdiscussed above. Furthermore, the invention may be adapted to generate avoice-guide message by combining simple phrases by the insertion ofconjunctions between phrases.

[0184] Furthermore, during voice guiding, the route from a presentposition to a guide point is displayed on the same screen. The positionof those nodes, links and related proximate facilities which correspondto information which voice guided may be displayed in a different colorfrom other parts or may be displayed by a blinking light.

[0185] As shown above, the present invention is adapted for use in anavigation device in which the level of importance of each node and linkis stored as a part of map information in a map information storagemeans. Nodes and links from amongst the nodes and links on the searchedroute are selected on the basis of the level of importance and a voiceguide message is generated which corresponds to the selected nodes andlinks. Thus, it is possible to guide an entire route appropriately in ashort time by voice and it is possible for a user to easily arrive at adestination.

What is claimed is:
 1. A navigation device comprising a map informationstorage means for storing map information including node information,link information and related information thereof, a present positiondetection means for detecting a present position of a moving body, aroute searching means for searching a route from the present position toa guide point based on said map information, a voice guide messagegeneration means for generating a voice guide message corresponding tothe route searched by said route searching means, and a voice outputmeans for outputting the voice guide message, wherein: said mapinformation storage means stores a level of importance of each node andlink as a part of said map information; and said voice guide messagegeneration means selects the nodes and links on the searched route basedon said level of importance and generates the voice guide messagecorresponding to the selected nodes and links.
 2. A navigation deviceaccording to claim 1 , wherein said voice guide message generation meansselects said nodes and links on the searched route in such a manner thata level of importance of the selected nodes and links is less than orequal to a predetermined reference value and a number of the selectednodes and links is less than or equal to a predetermined referencenumber, and generates the voice guide message corresponding to theselected nodes and links.
 3. A navigation device according to claim 2 ,wherein when a plurality of nodes and links with the same level ofimportance exists and the number of the selected nodes and links is notequal to the predetermined reference number, said voice guide messagegeneration means deletes nodes and links, which are located near theguide point, from said plural nodes and links with the same level ofimportance in such a manner that the number of the selected nodes andlinks is equal to the predetermined reference number.
 4. A navigationdevice according to claim 2 , further comprising a reference valuesetting means for setting the predetermined reference value and areference number setting means for setting the predetermined referencenumber.
 5. A navigation device according to claim 1 , wherein said mapinformation storage means stores information about voice playing timesrelating to names of each node and link as a part of said mapinformation, and wherein said voice guide message generation meansselects said nodes and links on the searched route in order of highimportance in such a manner that the voice playing time for the voiceguide message is less than or equal to a predetermined reference valueand generates the voice guide message corresponding to said selectednodes and links.